Control apparatus



1940- w. H. F. SCHMIEDING 2,135,317

CONTROL APPARATUS 7 Filed Sept. 9, 1937 2 Sheets-Sheet 1 1940; w. H. F.SCHMIEDING 1 common Arrm'rus v Filed Sept. 9, 19:57 '2 Sheets-Sheet 2Patented Jan. 2, 1940 UNITED STATES CONTROL APPARATUS Warren H. F.Schmieding, Columbus, Ohio, as-

signor to Ranco Incorporated, Columbus, Ohio, a corporation of OhioApplication September 9, 1937, Serial No. 163,054

6 Claims.

The invention relates to control systems and more particularly tocontrol systems and apparatus for controlling fluid fuel burners and thelike.

a One of the objects of the present invention is to provide a controlsystem which includes an electrically operated safety mechanism which isenergized continuously during the operating period of the fuel burningdevice and which is capable of rendering the same inoperative after apredetermined period of operation, an ignition device and switchtherefor being also provided, said switch being operated by the safetymechanism after a predetermined period of operation of the ignitiondevice. A combustion responsive control is utilized to prevent thesafety mechanism from rendering the system inoperative in the event thatcombustion is established and maintained.

It is a further object of the invention to prom vide a time delay switchfor the system which causes a delay between successive energizations ofthe system, said time delay switch being operated to open circuitposition by the electrically operated safety mechanism prior to theoperation of the ignition switch and being maintained in such positionduring the normal operating perind of the system, the time delay switchbeing disposed so as to be closed by the safety mechanism subsequent tothe closure of the ignition switch to assure that the ignition device isin readiness for operation before energization of the system.

In order to carry out the above object it is a further object to providea holding switch and circuit therefor to shunt the time delay switch,

the holding switch and circuit maintaining the control system operativeafter the time delay switch has been opened by the electrically heat- M,ed safety mechanism. Upon deenergization of the system, the holdingcircuit is broken and the system cannot be reenergized until the safetymechanism closes the time delay switch to reestablish the startingcircuit.

It is a still further object of my invention to provide means renderedeffective upon deenergization of the system for preventing theelectrically operated safety mechanism from operating, when thecombustion responsive means is w ineffective."

Other and further objects and advantages will be apparent from thefollowing description, reference being had to the accompanying drawingswherein preferred forms of embodiment of the 55 present invention areclearly shown.

In the drawings:

Fig. l is a schematic wiring diagram of one form of control systemutilizing a two wire thermostat, the system being shown in operativeposition, and,

Fig. 2 is a schematic wiring diagram of an-- other form of controlsystem utilizing a three Wire thermostat, and including an ambienttemperature compensator in connection with the safety mechanism.

Referring to Fig. 1, one form of the present invention is shown whereinthe system is utilized to control a fuel burning device, for example, anoil burner. A transformer relay is utilized to supply low voltagecurrent to the secondary cirl5 cult of the system and also to functionas a relay for actuating various control switches. A room thermostat 22controls the normal operation of the system to cause the fuel burningdevice to be started and stopped when there is a demand for 20 heat andwhen that demand has been satisfied. The thermostat 22 is in series witha secondary coil 24 of the transformer relay 20. When there is a demandfor heat, for example, when the temperature, of the enclosure to beheated, falls below a predetermined figure, room thermostat 22 closes tocomplete the secondary circuit, which includes secondary coil 24, wire26, contacts 28 and 29 of the time delay switch 30, pigtail 32, heatingcoil 34, wire 36, thermostat 22 and wire 38. Completion of the secondarycircuit causes the transformer relay 20 to draw armature 40 upwardly toclose switches 42 and M. Closure of switch 42 completes the motor andignition circuit to start the system in operation, 4

which circuit will be traced hereinafter. Closure of switch 44 causes ashunt secondary circuit to be established, around the time delay switch30, including secondary coil 24, wire 26, wire 46, switch 44, wire 48,heating coil 34, wire 36, thermostat 22 and wire 38.

Normally the primary coil 52 of transformer relay 20 is continuouslyenergized. The circuit therefor is traced as follows: wire 50, coil 52,wire 66, safety switch 64 and wire 62. When the armature is attracted,due to the completion of the secondary circuit, the motor and ignitioncircuits are completed. The motor circuit includes, wires and 54, motor55, wire 10, switch 42, wires 68 and 55, safety switch 64 and wire 62.The motor 56, in an oil burning system, is utilized for pumping in theoil and air for the burner, it being understood that this mixture isproportioned so that it will be ignited by the spark from spacedelectrodes of the ignition device. The ignition circuit includes wires68, 64 and 58, ignition primary coil 68, wire I8, ignition switch I4,wires I2 and I8, switch 42, wires 68 and 66, switch 64 and wire 62. Itwill be understood that the ignition system includes the usual highvoltage secondary coil and electrodes. It'

will be apparent that current for the primary coil 52 of the transformerrelay, the motor and the ignition must flow through the safety switchcontact 64.

Thus when switch 42 is closed, by action of the transformer relay 28,both the motor 56 and the ignition primary 68 are energized, providing,of course, the safety switch 64 is in closed circuit position. It willbe noted that the motor and ignition primary are preferably in paralleland, therefore, are energized substantially simultaneously.

Completion of the secondary circuit, due to closure of thermostat 22,causes current to flow continuously through heating coil 34 as long asthe circuit is energized. Coil 34 is disposed in intimate heat transferrelation with a U shaped bimetallic strip or thermostat I8. Upon initialclosure of the circuit, the thermostat I8 is in such position that theassociated contacts 28 and 29 of time delay switch 38 are in closedcircuit position. This allows the secondary circuit to be completed,through the time delay switch 38, which causes the relay 28 to pick upits armature 48. Subsequent and continued heating of bimetal I8 causesthe same to deflect upwardly to open the time delay switch 38, however,the secondary circuit is now maintained operative due to the priorclosure of the holding switch 44 which is closed by the attraction ofarmature 48.

The thermostat 18 carries a push rod 88 on the upper or free endthereof, which rod has a shouldered portion 82. The shoulder 82 isdisposed to engage a pivotally mounted lever 84 which upon upwardmovement thereof actuates the ignition switch I4 to open circuitposition. Thus after the bimetal 18 deflects upwardly, due to continuedheating of coil 34, the ignition switch I4 is opened, to render theignition device inoperative after a predetermined period of operationthereof and subsequent to the opening of the time delay switch 38. a

The thermostat I8 is also utilized to operate the safety switch 64. Thefree end of bimetal I8 abuts the upper end of an operating lever 86 ofthe safety switch 64, which lever is biased to open circuit position ofthe switch by suitable means, for example, a spring 88. As long as theend of bimetal I8 abuts the upper end of lever 86, the safety switch ismaintained closed. It is apparent that if the fuel supply is previouslyignited it is desirable to maintain the safety switch closed and therebypermit continued operation of the system. In order to maintain thesafety switch closed during normal operation of the system, a combustionresponsive control 98 is provided, of any conventional type, forexample, a bimetallic thermostat. The control 98 is adapted to operate alatch lever 92 which is normally against the stop 94 when the combustionchamber is cold, and which lever 92 is displaced to a position againststop 96 after combustion has been established. The latch lever 92 isdisposed to engage the moving end of a pivotally mounted lever 98 whichis abutted by the upper end of push rod 88. Thus as thermostat I8deflects upwardly, the push rod 88 causes lever 98 to move upwardly and,if combustion is established, to engage the latch lever 92, which actionlimits further I8.

Any suitable well known type of slip clutch is disposed between thebimetal, of combustion control 98, and latch 92 so that the latch 92 ismoved in either direction in response to slight rise or lowering of thetemperature of the combustion control.

Since under normal conditions the combustion control 98 acts morerapidly than does bimetal 18, the latch lever 92 is in position to limitupward movement of lever 98 prior to the time that the lever isdisplaced to engage the latch lever 92. A similar condition is presentupon deupward movement of the bimetal 'energization of the system, thecombustion control moving the lever 92 out of engagement with lever 98before the bimetal I8 has cooled sufliciently to preclude thepossibility of operation of the safety switch 64.

In order to prevent the bimetal I8 from opening the safety switch 64,under deenergization of the system, a rod I88 is provided on lever 98which is disposed in the path of the armature 48. When the latter isreleased and drops downwardly, due to deenergization of the relay 28,the armature 48 engages rod I88 and thereby functions to prevent releaseof the safety switch upon deenergization of the system although thecombustion control 98 has cooled sufliciently to release latch lever 92from its engagement with lever 98.

Upon failure of combustion during an operating period of the system thecontrol 98 moves latch lever 92 out of engagement with lever 98 to allowthe thermostat I8 to move upwardly to release the safety switch 64. Thisaction is substantially simultaneous with the release of lever 98, sincethe coil 34 is continuously energized during operating periods of thefuel burner and causes thermostat I8 to be heated above the temperaturenecessary to operate the safety device 64. Upon release of the safetyswitch, a manual resetting operation is necessary before the system canbe reenergized.

When a power failure occurs, even if the same is momentary, armature 48drops downwardly to open the motor switch 42 and also open the holdingswitch 44. Under this condition. the system cannot be reenergized untilbimetal 18 cools sufiiciently to reengage contacts 28 and 29 of the timedelay switch 38, to reestablish the secondary starting circuit. Itshould be noted that the ignition switch I4 is always closed prior tothe closure of the time delay switch, which assures that the ignitiondevice will be in readiness to function upon reenergization of thesystem.

If the fuel fails to ignite upon initial energization of the system, thebimetal I8 continues to move upwardly until the safety switch 64 isreleased to open. In this case the combustion control 98 isnon-operative to displace the latch lever 92.

Referring to Fig. 2, a similar system is shown except that a three wirethermostat is utilized. Since the high voltage circuits, which includethe motor and ignition devices, are similar to the high voltage circuitexplained in Fig. l, a detailed explanation thereof will be omitted.

The starting secondary circuit may be traced as follows: secondary coil24, wire I84, heating coil I86, which is connected to the bimetal I88,contacts I89 and- H8 of time delay switch II 2, wire II4, contacts I I6and I I8 of thermostat I82 and wire I28. Upon closure of the secondarycircuit, the transformer relay 28 is energized to Mil till

fih

draw armature 40 upwardly and close the high voltage circuit switch 42,and the holding switch 44. The closure of switch 44 completes thesecondary holding circuit, which may be traced as follows: secondary 24,wire I04, heating coil I00, bimetal I08, wire I22, switch 44, wire I24,bimetal I26, contacts I20 and H8 of thermostat I02 and wire I20. Afterthis secondary holding circuit is completed, due to the energization ofthe transformer relay 20, the time delay switch H2 may be opened withoutdeenergizing the circuit, which is now maintained through switch 44.

The function and operation of the various switches included in theaforementioned secondary circuits of this system is similar to thatdescribed in connection with Fig. 1.

It will be noted that in order to start the system by energizing thesecondary circuit, it is necessary to have all three contacts ofthermostat I02 in engagement. However, upon closure of switch 44 it isonly necessary to have contacts lit and I28 in engagement. This type ofthermostat is well known and, therefore, further explanation of the sameis unnecessary.

In the present embodiment an ambient temperature compensator is providedfor the bimetal I00, which actuates the safety switch 64. Thecompensator consists of a U shaped bimetal I30, similar in shape tobimetal I08 and fixedly mounted at one end thereof as at I32. The otherend of bimetal I30 is resiliently connected to bimetal IOB by a doubleheaded rivet I34, which passes loosely through both bimetals, and aspring I36 which is disposed around the rivet I34, and compressedbetween the bimetals I08 and I30. When room temperature is increased,for example, bimetal I08 deflects upwardly while bimetal I30, which isformed in the opposite direction, deflects downwardly the same or acomputed distance to translatably displace bimetal I08 so that theabutting end thereof is substantially unmoved with respect to itsposition relative to the end of the lever 86. In this manner the bimetalI08 is always maintained in substantially the same position regardlessof variations in ambient temperature and thus, the operating times ofthe switches operated thereby are maintained substantially constantregardless of variations in ambient temperature.

In both embodiments the electrically heated thermostat operates the timedelay switch, the ignition switch and the safety switch in the ordernamed and upon cooling, reverses the aforementioned sequence for closingthe ignition switch and the time delay switch.

From the foregoing it will be noted that the present invention providesa thermostatically operated safety switch that is in constant readinessto operate upon failure of combustion. The heating coil therefor iscontinuously energized during operating periods of the fuel burningdevice so that the thermostatic element is constantly heated and under asmall amount of stress when latched by the combustion control. Thisstress factor permits substantially simultaneous release of the safetyswitch when the combustion control unlatches the thermostatic member dueto failure of combustion. The present invention also provides latchingmeans operative upon deenergization of the system to latch or hold thethermostatic member from releasing the safety switch. This, aspreviously explained, is necessary since the combustion controlunlatches the thermostatic member before it has cooled to a temperaturesufficiently low to assure that it will not release the safety switch.

It is well known, that at times during the starting of an oil burner,the fuel mixture does not burn steadily and at times the fire isextinguished, but if a spark is provided, the mixture will readilyreignite and the burner would continue to function properly. In thepresent invention. the ignition circuit is maintained for a period ofninety to one hundred and twenty seconds, which period is sufficient tooverlap the unsteady starting period of the burner. If the mixture doesnot stay ignited during the selected period of between ninety and onehundred and twenty seconds, some adjustment must be made and in thatevent the safety switch functions substantially immediately todeenergize all the circuits thus insuring safety.

While the forms of embodiment of the present invention as hereindisclosed constitutes preferred forms, it is to be understood that otherforms might be adapted, all coming within the scope of the claims whichfollow:

I claim:

1. A control system for a fuel burning device comprising in combination,electrically operated means for controlling the fuel burning device; asafety switch operable to render the fuel burning device inoperative;electrically heated thermal means operable after a predetermined periodof heating to operate the safety switch, said thermal means being heatedcontinuously during the operating period of the fuel burning device,means for preventing operation of the safety switch by the thermalmeans, said last means being rendered efiective upon the establishmentof combustion and prior to the operation of the safety switch by thethermal means; and means rendered effective upon deenergization of theelectrically operated means for preventing operation of the safetyswitch by the thermal means when said combustion responsive means isineffective.

2. A control system for a fuel burning device comprising in combination,electrically operated means for controlling the fuel burning device; asafety switch operable to render the fuel burning device inoperative; anignition device for igniting the fuel; an ignition switch forcontrolling the operation of said ignition device; electrically heatedthermal means operable after a predetermined period of heating tooperate first the ignition switch and then the safety switch, saidthermal means being heated continuously during the operating period ofthe fuel burning device; means for preventing operation of the safetyswitch by the thermal means, said last means being rendered effectiveupon the establishment of combustion and prior to the operation of thesafety switch by the thermal means; and means rendered effective upondeenergization of the electrically operated means for preventingoperation of the safety switch by the thermal means when said combustionresponsive means is ineffective. 5

3. A control system for a fuel burning device comprising in combination,electrically operated means for controlling the fuel burning device; acircuit for said means; a time delay switch operable to deenergize thecircuit for the electrically operated means; an ignition device forigniting the fuel; an ignition switch for controlling operation of theignition device; a safety switch operable to render the fuel burningdevice inoperable; electrically heated thermal means operable afterpredetermined periods of heating to operate the time delay switch, theignition switch, and the safety switch, said last means being heatedcontinuously during the operating period of the fuel burning device;means rendered effective upon energization of the electrically operatedmeans for nullifying the effect of the time delay switch on saidcircuit, whereby the electrically operated means are maintainedoperative; means rendered effective upon the establishment ofcombustion, and prior to the operation of the safety switch, forpreventing operation of the safety switch by the thermal means; andmeans rendered effective upon deenergization of the electricallyoperated means for preventing operation of the safety switch by thethermal means when said combustion responsive means is ineffective.

4. A control system for a fuel burning device comprising in combination,electrically operated means for starting and stopping the fuel burningdevice; a safety switch operable to render the fuel burning deviceinoperative; means operable to actuate the safety switch after theelectrically operated means is operated to start the device, andoperable to actuate the safety switch for a predetermined period afterthe electrically operated means is operated to stop the device; meansfor preventing operation of the safety switch by the second mentionedmeans, the last mentioned means being effective upon the establishmentof combustion and prior to operation of the safety switch by the secondmentioned means; and means rendered effective upon stopping of thedevice for preventing operation of the safety switch by the secondmentioned means when said combustion means is ineffective.

5. A control system for a fuel burning device comprising in combination,electrically operated means for controlling the fuel burning device; asafety switch operable to render the fuel burning device inoperative;electrically heated thermal means operable after a predetermined periodof heating to operate the safety switch, said thermal means being heatedduring the operating period of the fuel burning device; means forpreventing operation of the safety switch by the thermal means, saidlast means being rendered effective upon the establishment of combustionand prior to the operation of the safety switch by the thermal means;and means rendered effective upon deenergization of the electricallyoperated means for preventing operation of the safety switch by thethermal means when said combustion responsive means is inefiective.

6. A control system for a fuel burning device comprising in combination,electrically operated means for controlling the operation of the de-vvice; a control circuit for the electrically operated means, saidcircuit including a delay switch and a control switch; a circuit forminga shunt around the delay switch, said shunt circuit including switchingmeans operated in response to energization of the control circuit forcompleting the shunt circuit when the electrically operated means isenergized and for opening the shunt circuit when the electricallyoperated means is deenergized; an ignition device for igniting the fuel;an ignition switch for controlling operationof the ignition device; asafety switch operable to render the fuel burning device inoperable; athird means, operable after predetermined periods after energization ofthe elec trically operated means for opening the delay switch, theignition switch and the safety switch and operable upon deenergizationof the burner device to first close the ignition switch and then thedelay switch; means responsive to combustion for preventing operation ofthe safety switch; said third means being operable to actuate the safetyswitch for a predetermined period after the electrically operated meansis operated to stop the device; and means rendered effective uponstopping of the device by the electrically operated means for preventingoperation of the safety switch by the third mentioned means.

WARREN H. F. SCHMIEDING.

